Prosthetic assemblies generally include a prosthetic limb and a socket which must be accurately positioned with respect to one another to achieve proper balance of the prosthetic limb. Depending upon the style, size, and weight of the prosthetic limb, the proper position with respect to the socket will vary. Early prosthetic assemblies comprised a prosthetic limb with a socket fixedly attached to the limb such that the relative positions of the limb and socket would be permanently set by the manufacturer.
Unfortunately, all users of prosthetic limbs are not built to the same proportions and small adjustments of the limb with respect to the socket are often necessary to achieve maximum comfort. In addition, prosthetic users often require a new socket due to a change in girth of the amputated stump. However, if the limb is permanently attached to the socket, the limb must also be replaced even though it is still satisfactory to the prosthetic user. Conversely, a prosthetic user may desire an updated limb and thus be forced to replace a comfortable and functional socket.
Therefore, newer prosthetic assemblies include separate limbs and sockets to allow a user to replace one without being forced to replace both. An adjustable connector assembly is provided to retain the socket and limb together and provide relative adjustment between the socket and limb. In this manner, limbs of varying design can be aligned perfectly with any socket to achieve proper balance and comfort.
Unfortunately, many modern connector assemblies are either very complex or provide a limited range of permissible adjustment. For example, U.S. Pat. No. 5,013,325 to Rennerfelt discloses a socket for a prosthetic assembly comprising an end plate and a cylindrical wall extending upwardly therefrom. A circular opening is disposed in the end plate, and a circular washer is disposed over the opening and against the end plate. A bolt extends through the washer and through the opening for attachment to a prosthetic limb. As the position of the limb is adjusted, the bolt and circular disc will move relative to the circular opening.
To achieve the maximum possible adjustment, the circular opening should be as large as possible to permit the bolt to have the widest range of movement. As the opening is expanded, however, the disc must also be expanded to remain larger than the opening. Unfortunately, the movement of the disc is restricted by the cylindrical wall of the socket and a large disc will have a small range of movement within the socket. Therefore, due to the competing constraints of disc size and opening size, maximum available adjustment is limited.